In a magnetic recording and/or reproducing apparatus, such as an audio tape recorder or a video tape recorder (VTR), the tendency is towards increasing the recording density and the quality of the recording signals. In keeping with such tendency towards increasing the recording density, a so-called metal tape in which powders of metals such as Fe, Co or Ni or alloys thereof are used as magnetic powders, or a so-called vapor-deposited tape in which a magnetic metal material is directly applied to a base film by a vacuum thin film forming technique, has been developed as the magnetic recording medium, and put into practical use in many fields.